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Solar energy conversion: Solar thermal Davide Del Col Department of Industrial Engineering
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Page 1: Solar energy conversion: Solar thermal

Solar energy conversion:

Solar thermal

Davide Del Col

Department of Industrial Engineering

Page 2: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Solar thermal collectors and applications

40°C – 80°C

Flat plate collectors

80°C – 120°C

Evacuated tube

collectors (with CPC)

120°C – 250°C

Small linear

concentrating

collectors

250°C – 450°C

Large troughs and

Fresnel

Solar tower in

heliostats field

Temperature

Size<10 kW 100 kW 10 MW 500 MW

Low temperature processes

Single effect absorption cooling

Space heating

Domestic hot water

Utility scale

solar power generation

MATURE

MATURE

Power generation with ORC

Industrial process heat

Double effect absorption

cooling

Water desalination

LOW

FAMILIARITY

AND LEVEL OF

ADOPTION

Page 3: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Applications for solar process heat

Source: Soltigua

Page 4: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Main topics and issues for research

Architectural integration of solar collectors (for low and medium

temperature applications)

Enhancement of performance, durability and cost effectiveness of the

collector (for all the applications)

> Improvement of collector component

Optimization of other components and configuration in plants using

common fluids (water, steam, thermal oil)

Design of new plant configurations for innovative applications with

uncommon working fluids (i.e. CO2)

Page 5: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

The building integration challengeFor low temperature applications

Source: Report IEA

Page 6: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

The building integration challengeInstallation on industrial rooftop for

medium temperature production

Source: Chromasun

Source: NEP Solar

Source: UNIPD

Page 7: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Optimizing collectors: flux mapping

Characterize the optical performance

Assess tracking system, mechanical

structure, durability

Design receivers with optimized and

advanced geometry

Develop of reliable models of the

system

Improve the aiming strategy (for

central receiver of heliostat fields)

Page 8: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Receivers with enhanced heat transferIn concentrating collectors, the solar flux distribution on the receiver surface is

strongly non uniform. This leads to:

thermal stresses and strains which may provoke mechanical instability

peak temperatures that damage the selective coating

instability and out-of-control of direct steam generation process

New solutions are required, especially for medium temperature applications

Page 9: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

The concept of volumetric absorptionVolumetric

(direct)

absorption

collectors

Typical

surface

absorption

collectors

Today nanotechnologies allow

the production of nanofluids

-with excellent optical properties

-stable

-safe and non toxic

Page 10: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Research activity overviewAim of the project

Analysis of the thermal performance of a volumetric receiver for heat

generation in the medium temperature range. The working nanofluid is an

aqueous suspension of single wall carbon nanohorns.

Comparison between the volumetric receiver and an advanced surface

absorption receiver in terms of performance, environmental and economical

aspects.

Performed activities

Measurement of concentrated flux distribution on the focal region of the

concentrator at CO.EN.SO lab

Experimental analysis of the performance of the advanced surface receiver

Design of the volumetric receiver

Preparation of the nanofluid, thermophysical and optical characterization

(collaboration with CNR)

Page 11: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Solar energy conversion lab

ASYMMETRICAL

PARABOLIC

TROUGH

2-axes tracking

aperture width: 2.9 m

trough length: 2.4 m

focal length: 1.81 m

Page 12: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Solar flux mapping apparatus

z

x

Parabolic

mirrors

z

x,z optimal concentration plane

semi automatic linear hangling system

+

water cooled heat flux microsensor (HFM)

x

Page 13: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Solar flux mapClear sky day DNI 890 W m-2

Page 14: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Study on a surface absorption receiverReceiver length: 1.2 m

width: 68 mm

Geometrical concentration ratio: 42

Internal turbulator for heat transfer

enhancement and efficient direct

steam generation

Test runs have been performed in two

modes

- liquid heating

- direct steam generation up to 140°C

Page 15: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Study on a surface absorption receiver

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14 0,16 0,18

Ov

era

ll t

he

rma

l e

ffic

ien

cy

[ /

]

Reduced temperature difference [ K m2 W-1 ]

single phase tests

two phase tests

efficiency curve (single phase tests only)

efficiency curve (all data)

Thermal efficiency of

66% when producing

steam at 140°C

It can be improved by

working on the

selective coating and

glass covering

Page 16: Solar energy conversion: Solar thermal

Levi Cases Retreat DayMonday, January 18th, 2016

Aula Magna – Pentagono – Agripolis, Legnaro (PD)

Design of a volumetric absorption

receiver and nanofluid preparation

Source: UNIPD

Source: CNR

Page 17: Solar energy conversion: Solar thermal

Thank you for your attention

Davide Del Col

[email protected]


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